Low pH, acid-containing personal care compositions have a variety of possible uses. Such compositions can potentially be useful for treatment of acne, treatment of dry skin, providing an essentially immediate (i.e., acute) visual improvement in skin appearance, regulating skin condition, and regulating visible and/or tactile discontinuities in skin. Perhaps most importantly, certain low pH, acid-containing compositions, especially those which also contain an antimicrobial agent, have been shown to have excellent antimicrobial efficacy.
Unfortunately, many useful acid-containing personal care compositions can cause an undesirable stinging sensation when they are applied to the skin. The problem can be especially exaggerated when the personal care composition contains high levels of acid (e.g., from about 4% to about 12% of the composition). The stinging sensation caused by these products can be a significant consumer negative; as a result of the stinging, some consumers may choose not to use a product they might otherwise have used and benefited from.
It is widely recognized that high levels of organic acids cause stinging. The patent literature has addressed the problem to a certain extent. For example, U.S. Pat. No. 4,975,217; issued Dec. 4, 1990 teaches the use of citric and lactic acid in virucidal formulas and teaches that citric acid stings less than lactic. European Patent Application 0,666,072 A2, published on Aug. 7, 1995 teaches that rosmarrinic acid can be employed in acid-containing compositions to reduce sting.
It has now been found, however, that sting is vastly reduced and, in some cases, completely eliminated when certain polymeric acids are employed in place of other organic acids in low pH, acid-containing personal care compositions. WO 95/32705, published Dec. 7, 1995, teaches generally the use of these polymeric acids, as well as other organic acids, in low pH, acid-containing personal care compositions. However, low pH, acid-containing personal care compositions which contain polymeric acids are not specifically taught and polymeric acids are not taught as reducing sting.
It is an object of the present invention, therefore, to provide low pH, acid-containing personal care compositions which cause significantly less stinging when they are applied to the skin compared to other low pH, acid-containing personal care composition taught in the prior art.